Max reports the maximum value in a given list. For example, show max [1 2 3] will return 3. Max is commonly used on a specific variable of an agentset, which would look like max [variable] of agentset. So
ask turtles with max [size] of turtles [ set color white ]
would set the largest turtle or turtles to white.
Once you mastered the max primitive, don't stop there. Check out the resources below to improve your NetLogo skills.
max primitive: